Changeset 14117

Timestamp:

Aug 5, 2010, 12:41:04 AM (9 years ago)

Author:

gb

Message:

Scheme for stack-overflow recovery (e.g., for re-protecting guard pages
after the stack is unwound past the point of overflow.)

A new TCR field, a new UUO, use of that UUO in nthrow subprims, handler
for the UUO.

Location:

branches/arm/lisp-kernel

Files:

• arm-constants.h (modified) (2 diffs)
• arm-constants.s (modified) (1 diff)
• arm-exceptions.c (modified) (6 diffs)
• arm-macros.s (modified) (1 diff)
• arm-spentry.s (modified) (5 diffs)
• arm-uuo.s (modified) (1 diff)

branches/arm/lisp-kernel/arm-constants.h

@@ -281 +281 @@
   struct tcr *prev;
   unsigned lisp_fpscr;
-  unsigned pad;
+  unsigned stack_overflowed;    /* non-zero when a stack has overflowed */
   special_binding *db_link;     /* special binding chain head */
   LispObj catch_top;            /* top catch frame */
@@ -345 +345 @@
 #define FPSCR_UFE_BIT 11                    /* underflow enable */
 #define FPSCR_IXE_BIT 12                    /* inexact enable */
+
+#define STACK_OVERFLOW_CSTACK fixnum_bitmask(0)
+#define STACK_OVERFLOW_VSTACK fixnum_bitmask(1)
+#define STACK_RECOVERY_MARGIN (8192)

branches/arm/lisp-kernel/arm-constants.s

@@ -588 +588 @@
          _node(next)            /* in doubly-linked list */
          _node(lisp_fpscr)      /* lisp thread's fpscr (in low word) */
-         _node(pad)
+         _node(stack_overflowed) /* Some stack has overflowed ;  maybe fix */
          _node(db_link)         /* special binding chain head */
          _node(catch_top)       /* top catch frame */

branches/arm/lisp-kernel/arm-exceptions.c

@@ -507 +507 @@
 signal_stack_soft_overflow(ExceptionInformation *xp, unsigned reg)
 {
-  /* The cstack just overflowed.  Force the current thread's
-     control stack to do so until all stacks are well under their overflow
-     limits. 
-  */
-
-#if 0
-  lisp_global(CS_OVERFLOW_LIMIT) = CS_OVERFLOW_FORCE_LIMIT; /* force unsigned traps to fail */
-#endif
+  
   handle_error(xp, error_stack_overflow, reg, NULL);
 }
@@ -928 +921 @@
   protected_area_ptr vsp_soft = a->softprot;
   unprotect_area(vsp_soft);
+  tcr->stack_overflowed |= STACK_OVERFLOW_VSTACK;
   signal_stack_soft_overflow(xp,vsp);
   return 0;
@@ -937 +931 @@
 do_soft_stack_overflow(ExceptionInformation *xp, protected_area_ptr prot_area, BytePtr addr)
 {
+  TCR *tcr = get_tcr(true);
+
   /* Trying to write into a guard page on the vstack or tstack.
      Allocate a new stack segment, emulate stwu and stwux for the TSP, and
@@ -945 +941 @@
   }
   unprotect_area(prot_area);
+  tcr->stack_overflowed |= STACK_OVERFLOW_CSTACK;
   signal_stack_soft_overflow(xp,Rsp);
   return 0;
@@ -1045 +1042 @@
   opcode *there = (opcode *) where, instr, errnum = 0;
   return err;
+}
+
+Boolean
+try_stack_overflow_recovery(ExceptionInformation *xp, TCR *tcr)
+{
+  area *a;
+  protected_area_ptr soft;
+
+  if ((tcr->stack_overflowed) & STACK_OVERFLOW_CSTACK) {
+    a = tcr->cs_area;
+    soft = a->softprot;
+    if (((BytePtr)xpGPR(xp,Rsp)-STACK_RECOVERY_MARGIN) >
+        (soft->end)) {
+      protect_area(soft);
+      tcr->stack_overflowed &= ~STACK_OVERFLOW_CSTACK;
+    }
+  }
+
+  if ((tcr->stack_overflowed) & STACK_OVERFLOW_VSTACK) {
+    a = tcr->vs_area;
+    soft = a->softprot;
+    if (((BytePtr)xpGPR(xp,vsp)-STACK_RECOVERY_MARGIN) >
+        (soft->end)) {
+      protect_area(soft);
+      tcr->stack_overflowed &= ~STACK_OVERFLOW_VSTACK;
+    }
+  }
 }
 
@@ -1131 +1155 @@
       handled = true;
       break;
+    case 6:
+      try_stack_overflow_recovery(xp,tcr);
+      handled = true;
+      break;
     default:
       handled = false;

branches/arm/lisp-kernel/arm-macros.s

@@ -498 +498 @@
         ')                
 
+/* Check to see if we've unprotected a stack region in response to an overflow ;
+   if so, trap into the kernel to see if that region can be protected again. */
+define(`check_stack_overflow_recovery',`
+        __(ldr $1,[rcontext,#tcr.stack_overflowed])
+        __(cmp $1,#0)
+        __(uuo_stack_overflow_recovery(ne))
+        ')
+        

branches/arm/lisp-kernel/arm-spentry.s

@@ -3921 +3921 @@
         __(ldr lr,[sp,#catch_frame.size+lisp_frame.savelr])
         __(add sp,sp,#catch_frame.size+lisp_frame.size)
+        __(check_stack_overflow_recovery(imm0))
         __(bx lr)
 _endfn(C(_throw_found))        
@@ -3949 +3950 @@
         __(ldreq vsp,[sp,#catch_frame.size+lisp_frame.savevsp])
         __(add sp,sp,#catch_frame.size+lisp_frame.size)
+        __(check_stack_overflow_recovery(arg_y))
         __(b local_label(_nthrow1v_nextframe))
 local_label(_nthrow1v_do_unwind):
@@ -3969 +3971 @@
         __(ldr vsp,[temp0,#lisp_frame.savevsp])
         __(mov fn,nfn)
+        __(check_stack_overflow_recovery(arg_y))        
         __(str imm1,[rcontext,#tcr.unwinding])
         __(blx lr)
@@ -4023 +4026 @@
 local_label(nthrownv_skip):     
         __(add sp,sp,#catch_frame.size+lisp_frame.size)
+        __(check_stack_overflow_recovery(arg_y))        
         __(b local_label(nthrownv_nextframe))                
 local_label(nthrownv_do_unwind):
@@ -4056 +4060 @@
         __(str fn,[arg_z,#lisp_frame.savefn])
         __(ldr vsp,[arg_z,#lisp_frame.savevsp])
+        __(check_stack_overflow_recovery(arg_y))        
         __(str imm1,[rcontext,#tcr.unwinding])
         __(mov fn,nfn)

branches/arm/lisp-kernel/arm-uuo.s

@@ -83 +83 @@
 define(`uuo_interrupt_now',`nullaryUUO($1,4)')
 define(`uuo_suspend_now',`nullaryUUO($1,5)')
-
+define(`uuo_stack_overflow_recovery',`nullaryUUO($1,6)')
+        
 /* Unary UUOs */
 define(`uuo_error_unbound',`unary_errorUUO($1,$2,0)')